1. Field of the Invention
The present invention relates to forming tools for performing forming work on a sheet workpiece, and in particular to forming tools where a punch and a die are made common in their structural components and the punch and the die can alternately be detachably exchanged to an upper holder and a lower holder, and which are detachably exchangeable to such a conventional punch press as a turret punch press like conventional tools.
2. Description of the Related Art
As a conventional example relating to the present invention, there is, for example, Japanese Patent Application Laid-Open No. 62-234622. The above conventional example is configured such that a punch and a die are detachably exchangeable to an upper holder and a lower holder alternately.
In the conventional example, since the punch and the die have structures completely different from each other and they have no common structural part or portion, the punch and the die must be manufactured fully independently from each other, and they have expensive structures (which results in increase in manufacturing cost). Also, fixing of the punch or the die to the upper holder is performed by a plurality of fixing screws, and the fixing screws project from an outer peripheral face of the upper holder. Therefore, there is a problem that, when the upper holder is mounted on an upper tool supporting member movably in a vertical direction, the fixing screws are obstructive so that the entire structure of the punch press is large-sized in a vertical direction.